diff --git a/content/canvas/test/webgl/test_webgl_conformance_test_suite.html b/content/canvas/test/webgl/test_webgl_conformance_test_suite.html
index d1172abe39e0..be6149abe660 100644
--- a/content/canvas/test/webgl/test_webgl_conformance_test_suite.html
+++ b/content/canvas/test/webgl/test_webgl_conformance_test_suite.html
@@ -372,9 +372,12 @@ function start() {
     try {
       netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
       var version = Components.classes["@mozilla.org/system-info;1"]
-                              .getService(Components.interfaces.nsIPropertyBag2)
-                              .getProperty("version");
-      is106orHigher = (parseFloat(version) >= 10.6);
+                              .getService(Components.interfaces.nsIPropertyBag2)
+                              .getProperty("version");
+      // the next line is correct: Mac OS 10.6 corresponds to Darwin version 10 !
+      // Mac OS 10.5 would be Darwin version 9. the |version| string we've got here
+      // is the Darwin version.
+      is106orHigher = (parseFloat(version) >= 10.0);
     } catch (ex) { }
     if (!is106orHigher) {
       dump("WebGL mochitest disabled on Mac OSX versions older than 10.6");